Chain conveyor in the form of scales

ABSTRACT

A chain conveyor for gravimetrically measuring/dosing materials, especially bulk materials. The conveyor includes a housing/trough in which at least two chain conveyors with strip-shaped driving elements attached thereto rotate, wherein a measuring bridge that is supported on at least one force measuring device is arranged between the inlet and an outlet hole. The driving elements are mounted with multiple articulations on the conveyor chains, more particularly, said driving elements are inserted with positive-fit by lateral hinge bolts in the chain links located on the upper edge and configured to be placed flatly in the measuring bridge.

RELATED APPLICATIONS

This application is the U.S. National Phase of PCT/EP02/07018 filed Jun.25, 2002 and claims priority to German Patent Application No. 101 30022.0 filed Jun. 25, 2001, which are hereby incorporated herein byreference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a chain conveyor for gravimetricallymeasuring/dosing materials, especially bulk materials, with saidconveyor comprising a housing/trough in which at least two conveyorchains with strip-shaped driving elements attached thereto rotate, aswell as an inlet/filling opening and an outlet opening in thehousing/trough, with at least one measuring bridge (2) which issupported on at least one force measuring apparatus is arranged betweenthe inlet/filling and outlet opening.

2. Description of the Related Art

Such chain conveyors are used especially for conveying and weighing bulkmaterials. Such chain conveyors are also used increasingly in the basicindustry (e.g. in the production of cement) for dosing or detecting theconveying strength of bulk materials because they allow a wear-resistantconfiguration at high throughputs and high draw-off forces. Moreover,the chain conveyor is relatively cheap to produce and service and easyto mount, so that the same is also suitable as a bunker draw-off memberfor abrasive, coarse or adhesive bulk materials due to this sturdyconfiguration.

The disadvantageous aspect in the conventional arrangement of the chainconveyor is that the dosing precision can be relatively low when theconveyed material sticks to the driving element webs during the emptyingor when disturbing forces from the conveyor chains alter themeasurement. This can lead to significant deviations concerning thedosing precision, which is important however for mixtures of additives.Weighing machines are already known in conjunction-with belt conveyorsor even discharging plate conveyors (e.g. according to DE 195 36 871 orDE 42 30 368), with the conveyor belt or the discharging plate conveyorbelt extending over a stationary weigh-bridge. These conveyors come withdisadvantages relating to the wearing behavior or the required powerconsumption because conveyor belts made of rubber materials are subjectto high wear and tear even in reinforced configuration on the one hand,whereas on the other hand discharging plate conveyor belts show highfriction due to the relative movement between the individual joints,especially under high load.

SUMMARY OF THE INVENTION

The invention is therefore based on the object of improving the dosingprecision of chain conveyors in combination with a simple design.

As a result of the multiple articulations of the “trailing” or draggingarranged driving elements, driving elements are “uncoupled” in respectof weighing from the conveyor chains. As a result of this at leastdouble articulation of the driving elements on the conveyor chains, thedriving elements rest flat on the sliding surfaces of the weigh-bridge.Moreover, disturbing forces on the conveyor chains (e.g. when grainymaterial is clamped between the driving elements and the weigh-bridge)are substantially avoided, so that the measuring section per se is freefrom external forces. As a result of this height-movable guidance of thedriving elements (which are U-shaped in a top view) on the conveyorchains, a reliable and simple multiple uncoupling is obtained, with thedriving elements being driven in a secure fashion by the conveyor chainsin the rotating direction. In this way it is possible to securely avoidproblems with uneven conveyance as can occur in the rigid arrangement ofthe driving elements.

An especially simple embodiment of the proposed chain conveyor isobtained in such a way that the driving elements of the chain conveyorare swivelably arranged on a guide-bar-like or bracket-like holdingdevice. This arrangement is especially also suitable for retrofittingexisting chain conveyors because the simple fastening of the lateralhinge bolts allow retrofitting the chain conveyor (and even chain troughconveyors) with the gravimetric force measuring apparatus.

The same applies for the movable mounting of the driving elements whichare held in an uncoupled manner via further intermediate joints. Byinterposing such intermediate joints, especially simple hinges or chainlinks which are arranged in an upright fashion, a kind of “cardanic”mounting is obtained and thus an automatic centering of the drivingelements as conveying tools. Moreover, when arranging lateral limits onthe driving elements the conveyor chains run outside of the train ofbulk material, so that wear and tear can be reduced substantially.

BRIEF DESCRIPTION OF THE DRAWINGS

A special advantage is the recirculation of material which can thus beachieved, so that abraded pieces of bulk material and so-called ejectedgrain can be returned to the inlet opening.

Further advantageous arrangements are shown in the description below ofembodiments shown in the drawings, wherein:

FIG. 1 shows a chain conveyor scale in a side view;

FIG. 2 shows a sectional view of the chain conveyor scale according toFIG. 1 in an enlarged perspective view;

FIG. 3 shows a pertinent top view according to FIG. 2;

FIG. 4 shows a further representation of the side region of the chainconveyor as shown in FIG. 3;

FIG. 5 shows a further modified arrangement of the holding deviceaccording to FIGS. 3 and 4, and

FIG. 6 shows a sectional view of the end zones of the chain conveyor ina side view.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1 and 2 show a side view and a perspective view of a chainconveyor 1 in a housing or trough 3 which comprises a straight measuringsection or measuring bridge 2 which is arranged on the upper run 5 ofthe belt. Conveyor chains 6 run along the measuring bridge 2 in ahousing/trough 3, which conveyor chains comprise U-shaped conveyingtools (in the top view) or driving elements 7. As a result of thesedrag-link driving elements 7, the bulk material which enters the housing3 through an opening E (which in this case is a bunker or silo) isconveyed along the measuring bridge 2 in the carrying run 5 of the beltand then along the lower run 4 in a clockwise manner to an outletopening 9, as is indicated here with the arrows. Between theinlet/filling opening E and the outlet opening 9 the plate-likemeasuring bridge 2 is held in a movable or slightly resilient fashion bymeans of flexible intermediate elements and is supported in this respecton a force measuring apparatus 12 which is arranged at least below themeasuring bridge and supports in particular an approximately centrallyarranged weighing cell. A drive 13 is provided adjacent to the left endof the measuring bridge, which drive is provided in the form of a chainwheel which engages in the conveyor chains 6.

After the conveyance along the measuring section/measuring bridge 2, theconveyed bulk material (which is indicated with the dotted line) reachesa wear-proof base plate in the front discharge end before the drive 13in the region of the lower run 4 and finally the outlet opening 9 underhorizontal conveyance with the mutually parallel extending conveyorchains 6 and the bracket-like drive elements 7 where it can fall outunder the influence of gravity or can also be blown out. Notice must betaken that such a blow-out line (not shown) can be arranged in thehousing 3 (especially in the case of a pressure-tight or dust-proofarrangement of the chain conveyor). No disturbing moments are exerted onthe force measuring apparatus 12. Moreover, it can be used to performthe cleaning of the conveyor chains 6 and/or the driving elements 7.

Relevant is also the guidance along the housing bend 15 which is on theright in this case, because it can be used to upwardly recirculate anybulk material that may not have been ejected (cf. FIG. 6). Transverseforce sensors or weighing cells on inductive, capacitative orpiezoelectric basis can be used as force measuring apparatuses 12 forthe measuring bridge. Preferably, a virtually pathless measuring forcemeasuring apparatus 12 (especially a strain-gauge weighing cell) is usedbecause this allows limiting the bend angle of the measuring bridge 2 toa few angular minutes, so that the circulatory movement of the conveyorchains 6 is practically not obstructed.

The force measuring apparatus 12 conducts the measured values on theconveyed weight of the bulk material to a computer which calculates themomentary flow rate by forming the product from the measured valuestogether with the speed values which are obtained for example from atachometer generator on drive 13. This actual value is compared fordosing purposes preferably with a predetermined setpoint value and inthe case of deviations the controllable drive 13 is readjusted in theknown manner.

FIGS. 2 and 3 show the side region of the driving elements 7 which areheld on guide-rod-like holding devices 8, with the “floating” plug-typeconnection of the hinge bolts 27 on one upright chain link each of theconveyor chain 6 being shown.

The relevant aspect is that the U-shaped driving elements 7 areheight-movable or height-swivelable with respect to the conveyor chains6 and the measuring bridge 2, so that occurring disturbing forces, ifany, are not included in the result of the measurement or can beeliminated by the measuring bridge 2. The driving elements 7 can beadditionally loaded by heavy-metal inserts or the like in order toachieve a defined bearing behavior. The conveyor chains 6 per se can beguided on both sides in guide elements 11 which are slotted in across-like manner, whereas the driving elements 7 are inserted with thehinge bolts 27 (see in particular FIGS. 3 to 5) into the upright chainlinks 26 on the side with loose fit, so that disturbing forces cannot bepassed on to the conveyor chains and the driving elements 7 rest in aplane and uncoupled in several ways (i.e. insat least two degrees offreedom) on the measuring bridge 2 or on their halves in the case of abent bridge.

It is possible to also omit the lateral guide function of the guideelements 11, so that the conveyor chain 6 can be hindered from liftingoff from the measuring section in an upwardly manner for example by asmooth strip, whereas the lower side of the conveyor chains 6 canrevolve on a PTFE strip on the measuring bridge 2. Rollers or wheels canalso be provided for the purpose of guiding and supporting the conveyorchains 6 on the measuring section.

As is indicated in FIG. 1 by the broken line, the outlet opening 9′ canalso be arranged below the filling opening E or close to the drive 13.The outlet opening 9 can also be followed by a second measuring bridge.This allows detecting the weight of the driving elements, so that theactually occurring quantity of transported bulk material can bedetermined at the outlet opening 9 by differentiation following acomparison of the two measured values of the measuring bridges. If bulkmaterial particles should adhere to the driving elements 7 or theconveyor chains 6, only the bulk material quantity is detected whicheffectively leaves the chain conveyor 1.

As indicated above, the vertical movement play of the driving elements 7is relatively small, as also the slight lateral mobility, so that therotary movement of the conveyor chains 6 is not obstructed. Instead, thedriving elements 7 are centered in the lateral direction. As is shown inFIGS. 4 and 5, drag-links 8′ are provided on the holding devices 8 asswivelable bearings for the driving elements 7, which links also allow acertain lateral mobility of a few millimeters. In the most simple ofconfigurations, the drag-link 8′ is formed by an upright chain linkfastened to the holding device 8 in the manner of a cardanic mounting(FIG. 4), with link bars of the parallelogram also being possible. Inthe arrangement according to FIG. 5 the swivelability of the drivingelements 7 in the direction of height (perpendicular to the drawingplane) about the axis of the drag-link 8′ is limited by a stop 8 b whichengages in an oblong hole of the holding device 8. Instead of thisbracket/bolt mounting it is also possible to provide other low-frictionbearings for forming the drag-link 8′. It can also be seen that thehinge bolts 27 are inserted here into every fourth chain link of theconveyor chains, with the distance between the hinge bolts 27 also beingallowed to be more than four chain links, so that the lateral boundaries7′ can extend in the manner of a boundary plate in a mutuallyoverlapping manner along the measuring bridge 2 in order to prevent anylateral discharge of the conveyed bulk material towards the conveyorchains 6.

FIG. 6 shows the two deflection regions of the chain conveyor 1. Anexcessive tilting of the driving elements 7 can be provided in the rightregion (drive wheel 13) during the transition from the upper run to thelower run by the said stops 8 b. Excessive friction on the housing canthus be excluded. At the opposite end (deflection wheel 14), the limitedswiveling movement of the driving elements 7 in combination with thehousing bend 15 is used for the upward recirculation of material. Adefined contact of the driving elements 7 on the housing bend 15 canalso be achieved in this case.

Notice must be taken that the measured values of the force measuringapparatus(es) 12 are supplied to a known electronic evaluation systemwith a computer for calculating the momentary conveying strengthcompiled of measuring bridge load and conveying rate and are comparedthere with the defined set-point values. By accelerating or braking thedrive 13 of the chain conveyor 1 (e.g. with electronic speed control)the desired conveying or dosing quantity (conveying strength orconveying capacity) can be adhered to precisely, even in the case ofmaterials that are difficult to convey such as clinker or hot bulkmaterials. The chain conveyor in the form of scales can also be providedwith a configuration that is completely dust-proof.

1. A chain conveyor for gravimetrically measuring/dosing materials,especially bulk materials, with said conveyor comprising ahousing/trough in which at least two conveyor chains with strip-shapeddriving elements attached thereto rotate, as well as an inlet/fillingopening and an outlet opening in the housing/trough, with at least onemeasuring bridge which is supported on at least one force measuringapparatus arranged between the inlet/filling and outlet opening,characterized in that the driving elements are mounted with multiplearticulations on the conveyor chains, and are inserted with lateralhinge bolts in a positive-fitting manner in upright chain links, and areconfigured to be placed flatly on the measuring bridge.
 2. A chainconveyor as claimed in claim 1, characterized in that the drivingelements are swivelably arranged on guide-bar-like-holding device.
 3. Achain conveyor as claimed in claim 2, characterized in that the holdingdevice comprises a drag-link, in the form of an upright chain link orlink bars of a parallelogram.
 4. A chain conveyor as claimed in claim 3,characterized in that the drag-link comprises at least one stop fordelimiting a vertical stroke of the respective driving element.
 5. Achain conveyor as claimed in claim 1, characterized in that the drivingelements comprise lateral boundaries forming a U-shape in a top view. 6.A chain conveyor as claimed in claim 5, characterized in that theboundaries correspond in the conveying direction approximately to thelateral length of the measuring bridge or are provided with anarrangement which is longer than the measuring bridge.
 7. A chainconveyor as claimed in claim 1, characterized in that the drivingelements are arranged in a trailing manner along the conveyor chains byat least two chain links relative to the hinge bolts.
 8. A chainconveyor as claimed in claim 1, characterized in that the drivingelements each comprise a top weight.
 9. A chain conveyor claimed inclaim 1, characterized in that the hinge bolts engage with an at leastlow loose fit in the conveyor chains.
 10. A chain conveyor as claimed inclaim 1, characterized in that the driving elements are provided with arecirculating arrangement in a deflection region-from lower run to upperrun.